A critical need of the digital video industry is the reliable maintenance of the perceived quality of video signals at various points in their creation, encoding, transmission, storage and display. Maintaining video quality requires measuring this quality--reliably, repeatably, and quickly. Current practice uses human observers to assess quality of displayed video, but it is impractical for humans to see into the middle of complicated networks used for video processing or transmission, where quality estimation is now needed to ensure quality is maintained for the end user and to identify sources of error. Therefore, video quality must be estimated automatically for any point throughout a video processing or transmission system.
U.S. patent application Ser. No. 09/055,076, filed Apr. 3, 1998, now U.S. Pat No. 6,137,904 discloses one approach to automated video quality estimation. In this approach, the signal under test (a video sequence) is compared to a reference copy of the same signal to determine the discriminability between these two signals in psychophysical units of Just Noticeable Differences (JNDs).
The reference-based approach to assessing video quality has proven to be accurate and robust in predicting human subjective ratings of video quality over a large range of distortion types and intended signals. However, in digital video networks for such applications as direct broadcast satellite (DBS), cable and Internet distribution, the intended signal (the "reference") is never or rarely available for comparison to the processed or transmitted signal. As such, the present technique is not practical for use in these applications.
Therefore, reliable techniques are needed to assess digital video picture quality under conditions in which a reference signal is not available.